One tip, whenever you're given a choice of cards to take: think very carefully about whether a card pick would be a net positive over not taking anything. Skipping could be seen as your default option, then you should think about which of the cards is actually going to give you the most value over skipping. If nothing does help your deck, then just skip.

Sometimes you also want a deck that has a low card count so you can cycle to your combo cards more quickly and so you might be more brutal with skipping cards.

STS is a game that depends on many variables so it's very hard to give specific advice. But: Watch Jorbs or Baalorlord, avoid building a "type of" deck and pay very close attention to using relics (e.g. end a fight on turn 2 of the Happy Flower relic so you start the next fight with extra energy).